8.8

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2026-29039

CVE-2026-29039: changedetection.io: XPath - Arbitrary File Read via unparsed-text()

changedetection.io is a free open source web page change detection tool. Prior to version 0.54.4, the changedetection.io application allows users to specify XPath expressions as content filters via the include_filters field. These XPath expressions are processed using the elementpath library which implements XPath 3.0/3.1 specification. XPath 3.0 includes the unparsed-text() function which can read arbitrary files from the filesystem. The application does not validate or sanitize XPath expressions to block dangerous functions, allowing an attacker to read any file accessible to the application process. This issue has been patched in version 0.54.4.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-29039

CVE-2026-29039:

8.8

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
changedetection.io	pip	<= 0.54.3	0.54.4

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is an arbitrary file read due to an XPath injection in the include_filters field. The root cause is the use of the elementpath library's XPath3Parser without disabling dangerous functions like unparsed-text(), which can access the local filesystem.

The analysis of the patch commit 417d57e5749441e4be9acc4010369bded805d66f reveals the exact locations of the vulnerability. The patch introduces a SafeXPath3Parser where unsafe functions are explicitly removed.

Two functions were identified as vulnerable:

changedetectionio.html_tools.xpath_filter: This is the core function where the malicious XPath is executed when a website check is performed. The patch replaces the unsafe XPath3Parser with the new SafeXPath3Parser, confirming this is where the exploit is triggered.
changedetectionio.forms.ValidateCSSJSONXPATHInput.__call__: This function is the validation step for the user-provided filter. It was also using the unsafe XPath3Parser to validate the expression, which means the malicious payload was not blocked at the input stage. An attacker could save a filter with a payload like xpath:unparsed-text('file:///etc/passwd'), which would then be executed by xpath_filter.

During exploitation, a profiler would likely show xpath_filter in the stack trace as it's the function that directly processes the malicious XPath and triggers the file read.

Vulnerable functions

xpath_filter

changedetectionio/html_tools.py

This function is the primary execution point of the vulnerability. It takes the user-supplied XPath filter and executes it using `elementpath.select`. Before the patch, it used `XPath3Parser` directly, which includes the dangerous `unparsed-text()` function, allowing an attacker to read arbitrary files from the filesystem.

ValidateCSSJSONXPATHInput.__call__

changedetectionio/forms.py

This function is responsible for validating the user's input for XPath filters. It failed to prevent malicious XPath expressions from being saved because it only checked for syntactical validity using the same vulnerable `XPath3Parser`. This allowed the malicious payload to be stored and later executed by `xpath_filter`.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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